%                           elevar.m
%  Scope:   This MATLAB macro computes the elevation angle, ECEF unit line-
%           of-sight vector and the range, when the ECEF user and satellite 
%           positions are known; WGS-84 constants are used.
%  Usage:   [eangle,ulos,range] = elevar(user,sv)
%  Description of parameters:
%           user   -  input, ECEF user position vector
%           sv     -  input, ECEF satellite position vector
%           eangle -  output, elevation angle in radians
%           ulos   -  output, ECEF unit line-of-sight vector
%           range  -  output, range from user to satellite 
%  Remark:  The components of the input vectors and the range should have the
%           same unit, e.g. meter, foot.
%  External Matlab macros used:  uverv, wgs84con
%  Last update:  05/22/99
%  Copyright (C) 1996-99 by LL Consulting. All Rights Reserved.

function [eangle,ulos,range] = elevar(user,sv)

ulos = sv - user;
range = sqrt(ulos' * ulos);
ulos = ulos / range;

w1 = uverv(user);
eangle = asin(w1' * ulos);